Wire forms the basic building block of the world's electric power system, including transformers, transmission and distribution systems, and motors. The discovery of revolutionary HTS compounds in 1986 led to the development of a radically new type of wire for the power industry; this discovery is the most fundamental advance in wire technology in more than a century. However, to date only short samples of the HTS tape used in the manufacture of next-generation HTS wires have been fabricated at high performance levels. In order for HTS technology to become commercially viable for use in the power generation and distribution industry, it will be necessary to develop techniques for continuous, high-throughput production of HTS tape.
Ion beam-assisted deposition processes, such as is described in Iijima, et al., U.S. Pat. No. 6,214,772, dated Apr. 10, 2001 and entitled “Process for Preparing Polycrystalline Thin Film, Process for Preparing Oxide Superconductor, and Apparatus Therefore,” has shown great promise in creating desirable buffer layer characteristics as a support for a functional layer of a ceramic superconducting material, such as yttrium-barium-copper-oxide (YBCO) atop the buffering layers of yttrium-stabilized zirconia (YSZ) and cerium oxide (CeO2).
During IBAD, a vacuum-deposition process that combines physical vapor deposition (PVD) with ion beam bombardment occurs: a vapor of coating atoms is generated with an electron beam evaporator or ion beam sputter source or magnetron sputter source and is deposited on a substrate. Ions are simultaneously extracted from a plasma from an ion source and accelerated into the growing PVD film at energies of a few hundred electron-volts (eV). The ions impart substantial energy to the coating and coating/substrate interface.
This achieves the benefits of substrate heating (which generally provides a denser, more uniform film) without significantly heating the substrate material and degrading bulk properties. The ions also interact with the coating atoms, driving them into the substrate and producing a graded material interface, which enhances adhesion. These factors combine to allow the deposition of uniform, adherent, low-stress films of virtually any coating material on most substrates. In addition, concurrent ion beam bombardment of a growing film has been shown to impart biaxial texture. IBAD has been specifically used for this purpose to achieve a high-degree of biaxial texture in materials used as buffer layers for HTS tapes.
Prior art IBAD processes, especially those used to achieve biaxial texture in buffer layers for HTS tapes are well known for their slow deposition rates. The deposition rates are excruciating slow, around 1 Angstrom/second. The low deposition rate severely restricts the throughput of the process. One possibility to increase the throughput is to increase the area of the deposition zone. The high-throughput continuous deposition of buffer layers necessary to enable cost-effective and, consequently, widespread adaptation of HTS materials in the electricity transmission/distribution industry necessitates an increase in the deposition zone that is achievable through the prior art.
It is thus an object of this invention to provide a high-throughput IBAD system that achieves a deposition zone of sufficient width to achieve optimum thin film characteristics atop multiple translating substrate tapes.